NAME

       system_safe,  system_execs,  system_nosh  -  execute  a  command with its arguments from a
       string without using a shell

SYNOPSIS

       #include <stdlib.h>
       #include <execs.h>

       int system_safe(const char *command);
       int system_execsp(const char *command);
       int system_execsa(const char *command);
       int system_execs(const char *path, char const *command);

       int system_execsrp(const char *command, int redir[3]);
       int system_execsra(const char *command, int redir[3]);
       int system_execsr(const char *path, char const *command, int redir[3]);

       int system_nosh(const char *command);
       int system_execsqp(const char *command);
       int system_execsqa(const char *command);

       int system_execsqrp(const char *command, int redir[3]);
       int system_execsqra(const char *command, int redir[3]);

       These functions are provided by libexecs. Link with -lexecs.

DESCRIPTION

       system_safe is a safe replacement for system(3) provided by the libc.  system_safe  parses
       the  command string and runs the command directly, without using a shell. The command must
       be specified as an absolute pathname. system_safe does not support variables as argument.
       Command arguments in args are delimited by space characters (blank, tabs  or  new  lines).
       Single or double quotes can be used to delimitate command arguments including spaces and a
       non quoted backslash (\) is the escape character to protect the next char.
       system_execsa is like  system_safe  supporting  also  variables  as  arguments.   When  an
       argument  of  a  command  is a dollar sign followed by a name (e.g. $USER) s2argv puts the
       output of  the  s2argv_getvar function instead. (It is  possible  for  example  to  assign
       s2argv_getvar=getenv.   For  security  reasons,  the  function  is NULL by default and all
       variables get replaced with an  empty  string.   Programmers  can  use  their  own  custom
       function instead)
       In  system_execsp  the  executable  file  is sought using the PATH environment variable as
       explained for execlp(3).
       system_execs requires the path of the executable to be specified as its first parameter so
       it does not use the PATH environment variable.
       system_execsr,  system_execsrp  and  system_execsra works as their couterparts without the
       'r', but they permit the redirection of standard input, output and error  streams.   Their
       last  parameter  is an array of three integers.  The standard input of the command will be
       redirected to redir[0] if it is positive, the standard output to redir[1]  if  it  is  not
       negative  and  different  from 1, the standard error to redir[2] if it is not negative and
       different from 2.
       system_execsra does not use the PATH  variable,  argv[0]  must  be  specified  as  a  full
       pathname.
       system_nosh,  system_execsqp,  system_execsqa, system_execsqrp and system_execsqra can run
       sequences of commands separated by semicolons (;).  The first command returning a non-zero
       exit status breaks the sequence.
       system_nosh  is  an  almost  drop  in  replacement  for  system(3)  provided  by the libc.
       (system_execsqp and system_nosh are synonyms).

RETURN VALUE

       These functions have the same return values of  system(3).  When  running  a  sequence  of
       commands, it returns the "wait status" of the first command returning a non-zero value. If
       the return value is zero it means that all the commands of the sequence succeeded.

EXAMPLE

       The following program shows the usage of system_nosh:

       #include <stdio.h>
       #include <unistd.h>
       #include <execs.h>

       #define BUFLEN 1024
       int main(int argc, char *argv)
       {
            char buf[BUFLEN];
            printf("type in a command and its arguments, e.g. 'ls -l'\n");
            while (fgets(buf, BUFLEN, stdin) != NULL) {
                 printf("Command: '%s' \n",buf);
                 system_nosh(buf);
                 printf("Command done\n");
            }
       }

SEE ALSO

       system(3),execs(3),s2argv(3)

BUGS

       Bug reports should be addressed to <info@virtualsquare.org>

AUTHOR

       Renzo Davoli <renzo@cs.unibo.it>